metamorphic
Quartzite (Yellow/Iron-stained Quartz)
Quartzite (primarily SiO2 with iron oxide impurities)
Hardness: 7 (Mohs scale); Color: Yellowish-tan to creamy white; Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Yellowish-tan to creamy white
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 (Mohs scale); Color: Yellowish-tan to creamy white; Luster: Vitreous to greasy; Crystal structure: Trigonal/Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.63 - 2.65
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. The individual quartz grains recrystallize into a locked mosaic. The yellow coloration is likely due to iron oxide staining from groundwater exposure over geological time.
Uses & applications
Commonly used as crushed stone for construction, road ballast, and decorative landscaping. High-purity quartzite is used to produce glass and metallic silicon.
Geological facts
Quartzite is so hard that it will scratch glass and steel. It is one of the most physically and chemically resistant rocks found at the Earth's surface, often forming ridges because it erodes much slower than surrounding rocks.
Field identification & locations
Identify in the field by its extreme hardness and 'sugary' texture on broken surfaces. It is found globally in mountainous regions and riverbeds. For collectors, look for pieces with visible internal fractures or unique coloration created by mineral seepage.
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